Welcome to the I Can't Sleep Podcast,
Where I help you drift off one fact at a time.
I'm your host,
Benjamin Boster,
And today's episode is about hot air balloons.
Thank you to Heather Lamora for sponsoring today's episode.
A hot air balloon is a lighter-than-air aircraft consisting of a bag called an envelope,
Which contains heated air.
Suspended beneath is a gondola or wicker basket,
And some long-distance or high-altitude balloons a capsule,
Which carries passengers and a source of heat,
In most cases an open flame,
Caused by burning liquid propane.
The heated air inside the envelope makes it buoyant,
Since it has a lower density than the colder air outside the envelope.
As with all aircraft,
Hot air balloons cannot fly beyond the atmosphere.
The envelope does not have to be sealed at the bottom,
Since the air inside the envelope is at about the same pressure as the surrounding air.
In modern sport balloons,
The envelope is generally made from nylon fabric.
And the inlet of the balloon,
Closest to the burner flame,
Is made from a fire-resistant material,
Such as Nomex.
Modern balloons have been made in many shapes,
Such as rocket ships in the shapes of various commercial products,
Though the traditional shape is used for most non-commercial and many commercial applications.
The hot air balloon is the first successful human-carrying flight technology.
The first untethered manned hot air balloon flight in the world was performed in Paris,
France,
By Jean-François Pilâtre de Rosiers and François Laurent d'Hollande on November 21st,
1783,
In the balloon created by the Montgolfier brothers.
Hot air balloons that can be propelled through the air,
Rather than simply drifting with the wind,
Are known as thermal airships.
A precursor of the hot air balloon was the sky lantern.
Zhuge Liang of the Shuhan Kingdom,
During the Three Kingdoms era,
220-280 CE,
Used these airborne lanterns for military signaling.
The Mongolian army studied Gongming lanterns from China and used them in the Battle of Lagnitsa,
During the Mongol invasion of Poland in the 13th century.
This is the first time ballooning was known in the Western world.
In the 18th century,
The Portuguese Jesuit priest Bartolomeu de Guzmão,
In colonial Brazil,
Envisioned an aerial apparatus named Passarola,
Which was the predecessor of the hot air balloon.
The Passarola was intended to serve as an air vessel in order to facilitate communication and as a strategical device.
In 1709,
John V of Portugal decided to fund Bartolomeu de Guzmão's project following a petition made by the Jesuit priest and an unmanned demonstration was performed at Casa da Índia in the presence of John V and the Queen,
Maria Anna of Austria,
With the Italian Cardinal Michelangelo Conti,
Two members of the Portuguese Royal Academy of History,
One Portuguese diplomat and one chronicler serving as witnesses.
This would bring some European attention to this event and this project.
A later article dated on October 20th,
1786 by the London Daily Universal Register would state that the inventor was able to raise himself by the use of his prototype.
Also in 1709,
The Portuguese Jesuit wrote short manifesto for those who are unaware that it is possible to sail through the element air.
He also left designs for a manned air vessel.
In the 1970s,
Balloonist Julian Knott hypothesized that the Nazca Line's geoglyphs,
Creation two millennia ago,
Could have been guided by the Nazca leaders in a balloon,
Possibly the earliest hot air balloon flights in human history.
To support this theory,
In 1975 he designed and piloted the Nazca prehistoric balloon,
Claiming to have used only methods and materials available to the pre-Inca Peruvians 1,
000 years ago.
The French brothers Joseph Michel and Jacques-Étienne Montgolfier developed a hot air balloon in Annonay-Ardèche,
France,
And demonstrated it publicly on September 19th,
1783,
Making an unmanned flight lasting ten minutes.
After experimenting with unmanned balloons and flights with animals,
The first balloon flight with humans aboard,
A tethered flight,
Performed on or around October 15th,
1783,
By Jean-François Pilote de Rosiers,
Who made at least one tethered flight from the yard of the Réveillon workshop,
In the Faubourg Saint-Antoine.
Later that same day,
Pilote de Rosiers became the second human to ascend into the air,
Reaching an altitude of 26 meters,
The length of the tether.
The first free flight with human passengers was made a few weeks later,
On November 21st,
1783.
King Louis XVI had originally decreed that condemned criminals would be the first pilots,
But de Rosiers,
Along with Marquis François de Lande,
Petitioned successfully for the honor.
The first military use of a hot air balloon happened in 1794,
During the Battle of Fleurus,
When the French used the balloon l'Entrepreneur for observation.
Modern hot air balloons,
With an onboard heat source,
Were developed by Ed Yost and Jim Winker,
Beginning during the 1950s.
Their work resulted in the first successful flight on October 22nd,
1960.
The first modern hot air balloon to be made in the United Kingdom,
Was the Bristol Bell,
Built in 1967.
Presently,
Hot air balloons are used primarily for recreation.
On November 26th,
2005,
Vijay Patsinghania set the world altitude record for highest hot air balloon flight,
Reaching 21,
027 meters.
He took off from downtown Mumbai,
India,
And landed 240 kilometers south in Panchale.
The previous record of 19,
811 meters had been set by Per Lindstrøm on June 6th,
1988,
In Plano,
Texas.
On January 15th,
1991,
Per Lindstrøm,
Born in Sweden but resident in the UK,
And Richard Branson of the UK,
Flew 7,
671.
91 kilometers,
From Japan to northern Canada,
In the Virgin Pacific Flyer.
With a volume of 74,
000 cubic meters,
The balloon envelope was the largest ever built for a hot air craft.
Designed to fly in the trans-oceanic jet streams,
The Pacific Flyer recorded the fastest ground speed for a manned balloon,
At 394 kilometers per hour.
The longest duration record was set by Swiss psychiatrist Bertrand Piccard,
August Piccard's grandson,
And Britain Brian Jones,
Flying in the Breitling Orbiter 3.
It was the first non-stop trip around the world by balloon.
The balloon left Chateau de Switzerland on March 1st,
1999,
And landed at 1.
02 a.
M.
On March 21st in the Egyptian desert,
500 kilometers south of Cairo.
The man exceeded distance,
Endurance,
And time records,
Traveling 19 days,
21 hours,
And 55 minutes.
Steve Fawcett flying solo exceeded the record for briefest time traveling around the world on July 3rd,
2002,
In his sixth attempt,
In 320 hours,
33 minutes.
Fyodor Kunyukov flew solo around the world on his first attempt,
In a hybrid hot air helium balloon,
From the 11th to the 23rd of July,
2016,
For a round-the-world time of 268 hours,
20 minutes.
A hot air balloon,
For manned flight,
Uses a single-layered fabric gas bag,
Lifting envelope,
With an opening at the bottom called the mouth or throat.
Attached to the envelope is a basket or gondola for carrying the passengers.
Mounted above the basket and centered in the mouth is the burner,
Which injects a flame into the envelope,
Heating the air within.
The heater or burner is fueled by propane,
A liquefied gas stored in pressure vessels,
Similar to high-pressure forklift cylinders.
Modern hot air balloons are usually made of materials such as ripstop nylon or Dacron,
A polyester.
During the manufacturing process,
The material is cut into panels and sewn together,
Along with structural load tapes that carry the weight of the gondola or basket.
The individual sections,
Which extend from the throat to the crown of the envelope,
Are known as gores or gore sections.
Envelopes can have as few as four gores or as many as 24 or more.
Envelopes often have a crown ring at the very top.
This is a hoop of smooth metal,
Usually aluminum,
And approximately 30 cm in diameter.
Vertical load tapes from the envelope are attached to the crown ring.
At the bottom of the envelope,
The vertical load tapes are sewn into loops,
That are connected to cables,
One cable per load tape.
These cables,
Often referred to as flying wires,
Are connected to the basket by carabiners.
The most common technique for sewing panels together is called the French Feld,
French Fell,
Or double lap seam.
The two pieces of fabric are folded over on each other at their common edge,
Possibly with a load tape as well,
And sewn together with two rows of parallel stitching.
Other methods include a flat lap seam,
In which the two pieces of fabric are held together simply with two rows of parallel stitching.
And a zigzag,
Where parallel zigzag stitching holds a double lap of fabric.
The fabric,
Or at least part of it,
The top one third for example,
May be coated with a sealer,
Such as silicone or polyurethane,
To make it impermeable to air.
It is often the degradation of this coating and the corresponding loss of impermeability that ends the effective life of an envelope,
Not weakening of the fabric itself.
Heat,
Moisture and mechanical wear and tear during setup and pack-up are the primary causes of degradation.
Once an envelope becomes too porous to fly,
It may be retired and discarded,
Or perhaps used as a rag bag,
Cold,
Inflated and open for children to run through.
Products for recoating the fabric are becoming available commercially.
A range of envelope sizes is available,
The smallest one-person basketless balloons called hoppers or cloud hoppers have as little as 600 cubic meters of envelope volume.
For a perfect sphere,
The radius would be around 5 meters.
At the other end of the scale,
Balloons used by commercial sightseeing operations may be able to carry well over two dozen people with envelope volumes of up to 17,
000 cubic meters.
The most used size is about 2,
800 cubic meters,
Allowing to carry 3 to 5 people.
The top of the balloon usually has a vent of some sort enabling the pilot to release hot air to slow an ascent,
Start a descend,
Or increase the rate of descend,
Usually for landing.
Some hot air balloons have turning vents,
Which are side vents that,
When opened,
Cause the balloon to rotate.
Such vents are particularly useful for balloons with rectangular baskets to facilitate aligning the wider side of the basket for landing.
The most common type of top vent is a disc-shaped flap of fabric called a parachute vent,
Invented by Tracy Barnes.
The fabric is connected around its edge to a set of vent lines that converge in the center.
The arrangement of fabric and lines roughly resembles a parachute,
Thus the name.
These vent lines are themselves connected to a control line that runs to the basket.
A parachute vent is opened by pulling on the control line.
Once the control line is released,
The pressure of the remaining hot air pushes the vent fabric back into place.
A parachute vent can be opened briefly while in flight to initiate a rapid descend.
Slower descents are initiated by allowing the air in the balloon to cool naturally.
The vent is pulled open completely to collapse the balloon after landing.
An older and presently less commonly used style of top vent is called a Velcro-style vent.
This,
Too,
Is a disc of fabric at the top of the balloon.
However,
Rather than having a set of vent lines that can repeatedly open and close the vent,
The vent is secured by hook and loop fasteners,
Such as Velcro,
And is only opened at the end of the flight.
Balloons equipped with a Velcro-style vent typically have a second maneuvering vent built into the side as opposed to the top of the balloon.
Another common type of top design is the smart vent,
Which,
Rather than lowering a fabric disc into the envelope as in a parachute type,
Gathers the fabric together in the center of the opening.
This system can theoretically be used for in-fly maneuvering,
But is more commonly used only as a rapid deflation device for use after landing of particular value in high winds.
Other designs,
Such as the pop-top and multi-vent systems,
Have also attempted to address the need for rapid deflation on landing.
But the parachute top remains popular as an all-around maneuvering and deflation system.
Besides special shapes for marketing purposes,
There are several variations on the traditional inverted teardrop shape.
The simplest,
Often used by home builders,
Is a hemisphere on top of a truncated cone.
More sophisticated designs attempt to minimize the circumferential stress on the fabric,
With different degrees of success depending on whether they take fabric weight and varying air density into account.
This shape may be referred to as natural.
Finally,
Some specialized balloons are designed to minimize aerodynamic drag in the vertical direction,
To improve flight performance in competitions.
Hot air balloon baskets are commonly made of woven wicker or rattan.
These materials have proven to be sufficiently light,
Strong,
And durable for balloon flight.
Such baskets are usually rectangular or triangular in shape.
They vary in size from just big enough for two people to large enough to carry 30.
Larger baskets often have internal partitions for structural bracing and to compartmentalize the passengers.
Small holes may be woven into the side of the basket to act as footholds for passengers climbing in or out.
Baskets may also be made of aluminum,
Especially a collapsible aluminum frame with a fabric skin,
To reduce weight or increase portability.
These may be used by pilots without a ground crew or who are attempting to set altitude,
Duration,
Or distance records.
Other specialty baskets include the fully enclosed gondolas used for around-the-world attempts,
And baskets that consist of little more than a seat for the pilot and perhaps one passenger.
The burner unit gasifies liquid propane,
Mixes it with air,
Ignites the mixture,
And directs the flame and exhaust into the mouth of the envelope.
Burners vary in power output.
Each will generally produce 2 to 3 MW of heat,
7 to 10 million BTUs per hour,
With double,
Triple,
Or quadruple burner configurations installed where more power is needed.
The pilot actuates a burner by opening a propane valve,
Known as a blast valve.
The valve may be spring-loaded so that it closes automatically,
Or it may stay open until closed by the pilot.
The burner has a pilot light to ignite the propane and air mixture.
The pilot light may be lit by the pilot with an external device,
Such as a flint striker or a lighter,
Or with a built-in piezoelectric spark.
Where more than one burner is present,
The pilot can use one or more at a time,
Depending on the desired heat output.
Each burner has a metal coil of propane tubing the flame shoots through to preheat the incoming liquid propane.
The burner unit may be suspended from the mouth of the envelope,
Or supported rigidly over the basket.
The burner unit may be mounted on a gimbal to enable the pilot to aim the flame,
And avoid overheating the envelope fabric.
A burner may have a secondary propane valve that releases propane more slowly,
And thereby generates a different sound.
This is called a whisper burner,
And is used for flight over livestock to lessen the chance of spooking them.
It also generates a more yellow flame,
And is used for night glows,
Because it lights up the inside of the envelope better than the primary valve.
Propane fuel tanks are usually cylindrical pressure vessels made from aluminum,
Stainless steel,
Or titanium,
With a valve at one end to feed the burner and to refuel.
They may have a fuel gauge and a pressure gauge.
Common tank sizes are 38,
57,
And 76 liters.
They may be intended for upright or horizontal use,
And may be mounted inside or outside the basket.
The pressure necessary to force the fuels through the line to the burner may be supplied by the vapor pressure of the propane itself,
If warm enough,
Or by the introduction of an inert gas such as nitrogen.
Tanks may be preheated with electrical heat tapes to produce sufficient vapor pressure for cold weather flying.
Warmed tanks are usually also wrapped in an insulating blanket,
To preserve heat during the setup and flight.
A balloon may be outfitted with a variety of instruments to aid the pilot.
These commonly include an altimeter,
A rate of climb vertical speed indicator known as a variometer,
Envelope air temperature,
And ambient air temperature.
A GPS receiver can be used to indicate ground speed.
Traditional aircraft speed indicators would be useless,
And direction.
Increasing the air temperature inside the envelope makes it less dense than the surrounding ambient air.
The balloon floats because of the buoyant force exerted on it.
This force is the same force that acts on objects when they are in water,
And is described by the Archimedes principle.
The amount of lift or buoyancy provided by a hot air balloon depends primarily upon the difference between the temperature of the air inside the envelope and the temperature of the air outside the envelope.
For most envelopes made of nylon fabric,
The maximal internal temperature is limited to approximately 120 degrees Celsius.
The melting point of nylon is significantly greater than this maximal operating temperature,
About 230 degrees Celsius.
But higher temperatures cause the strength of the nylon fabric to degrade more quickly over time.
With a maximal operating temperature of 120 degrees Celsius,
Balloon envelopes can generally be flown for between 400 and 500 hours before the fabric needs to be replaced.
Many balloon pilots operate their envelopes at temperatures significantly less than the maximum to extend envelope fabric life.
The density of air at 20 degrees Celsius is about 1.
2 kilograms per meter cubed.
The total lift for a balloon of 2,
800 meters cubed heated to 99 degrees Celsius would be 723.
5 kilograms.
This is just enough to generate neutral buoyancy for the total system mass.
Lift-off would require a slightly greater temperature,
Depending on the desired rate of climb.
In reality,
The air contained in the envelope is not at all the same temperature,
And so these calculations are based on averages.
For typical atmospheric conditions,
A hot air balloon heated to 99 degrees Celsius requires about 3.
91 meters cubed of envelope volume to lift 1 kilogram.
The precise amount of lift provided depends not only upon the internal temperature,
But the external temperature,
Altitude above sea level,
And humidity of the surrounding air.
On a warm day,
A balloon cannot lift as much as on a cool day,
Because the temperature required for launch will exceed the maximum sustainable for nylon envelope fabric.
Also,
In the lower atmosphere,
The lift provided by a hot air balloon decreases about 3% per 1,
000 meters of altitude gained.
